1. Field of the Invention
The present invention relates to a method for the continuous assembly of patterned strips.
It can be applied notably to the making of micromodules in integrated circuit form that go into the production of the portable flat cards known as "chip cards". In these cards, the micromodules are formed by a set of elements comprising: a chip in integrated circuit form, metal contacts used for the connection of the micromodule with external devices, linking wires to link the chip to the metal contacts and a protective coat formed by a resin covering the chip, the linking wires and, partially, the metal contacts.
2. Discussion of the Related Art
To manufacture a micromodule and then incorporate it into a card, a first known method consists in mounting the chip on a metal strip that has been pre-slotted in the form of a conductor grid, soldering the chip to a zone of this grid where it is connected by wires soldered to other zones of the grid, coating the chip and the wires with a drop of protective resin of the epoxy or silicone type in leaving the conductors of the grid partially bared, cutting up the metal strip into individual micromodules, each comprising a coated chip and bared external contacts and then bonding the micromodule to a surface cavity of a card made of plastic material in such a way that grid portions not coated with resin are flush with the surface of the card and constitute the external connector of the card.
According to a second method which is also known, the initial pre-cut metal strip is replaced with a metallized dielectric strip etched with a connection pattern to be determined. The dielectrical strip, in this case, forms the main support of the chip. The connections have a very small thickness and are obtained by the pre-deposition of a metal layer on the photo-etching plastic strip of this metal layer. The chip is connected by soldered wires to zones of the metallized layer.
These methods have a certain number of drawbacks. In the case of the use of a pre-cut metal strip, the encapsulation resin of the micromodule adheres poorly to the conductors of the grid, all the more so as, in practice, the resin is on only one side of the strip, the other side being reserved to leave the conductors accessible to act as connectors. The result thereof is a problem of reliability that is difficult to resolve, caused chiefly by the passage of moisture between the resin and the conductors.
In the case of the use of a metallized and photo-etched dielectric strip, the strip musk necessarily be made of a sufficiently rigid material, and must stand up well to temperature so as not to get warped when the temperature rises, which makes it necessary for the definition of the conduction pattern to be executed only by photo-etching on the dielectric strip and makes this second method far costlier than a mechanical cutting-out operation for example.
A third method is known through the European patent application published under No. 0 296 511 and filed under No. 88 1097430 on 18th Jun. 1988.
This patent application relates to a method for the manufacture of a ribbon designed to provide modules to equip electronic cards also called "smart cards". However, the approach proposed in this patent application is not satisfactory.
Indeed, this method entails taking a metal strip with a thickness that is typically equal to 75 micrometers but may vary between 50 micrometers and 150 micrometers. This strip is provided with perforations enabling it to be carried along and apertures obtained by stamping that demarcate the arrays of conductors of the circuits. A set of 125-micrometer-thick insulating foils having, on one face, a thermoplastic or thermosetting material for hot bonding, is also taken. The foils have a set of holes with an arrangement that corresponds to the location of the connections and a central hole for the location of the circuit.
The foils are bonded to the metal strip by heating. The heating prompts a certain shrinkage of the insulator material which makes it difficult to use bigger foils, especially in the longitudinal direction. With cold bonding, the problem would not arise. By contrast, the adhesion to the metal is poor.
Furthermore, it is imperatively necessary to make a perforation in each insulator foil at the position reserved for the circuit in order to house the circuit therein and thus keep within the requisite tolerances as regards thickness for the manufacture of the chip cards.
Reference could also be made, as part of the prior art, to the document GB 2031796 A which describes a device for the assembling of an adhesive insulator strip to a conductive strip. In the device described, the adjusting of the tension is done only on the insulator strip by modifying the rotational speed of the wheels between which this strip passes. A device such as this does not enable the use of very thin 30 to 50 .mu.m insulator strips as is made possible by the invention.